The Mechanism of Ciliary Movement. 131 



(v) The action of solium salts can be inhibited by magnesium or by 

 calcium. Probably in normal sea-water the stability of the cell-membrane 

 is due to magnesium and not to calcium. 



(vi) In balanced solutions the monovalent cations have a direct effect 

 upon the rate of ciliary movement. The rate of movement in solutions 

 of the same hydrogen ion concentration is slowest in lithium and fastest 

 in potassium. The ions can be arranged in the following well-marked 

 series : — 



Li', Na\ NH 4 \ K\ 



(vii) The normal semipermeability of the cell- wall is not an essential 

 condition for ciliary movement. 



(viii) The way in which solutions of the different metals affect the cell- 

 surface is in complete agreement with the effect which they produce on the 

 electrical conductivity of the cell. 



(ix) There is a marked analogy between the action of salts on the livin g 

 cell-membrane and on a cholate gel, or oil and water emulsion. 



The expenses of this research were in part met by a grant from the 

 Government Grant Committee of the Eoyal Society. 



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